1. Field of the Invention
The present invention relates to a method for judging track addresses of a desired track, in an optical information recording and reproducing (playback) apparatus which simultaneously executes at least one of recording and reproducing of information with respect to a plurality of tracks.
2. Description of the Related Art and Prior Art Statement
A recording medium such as an optical card, an optical disc or the like has a plurality of tracks extending in parallel relation to each other, or extending in concentric relation to each other. On the other hand, an optical information recording and reproducing apparatus comprises an optical head for optically recording/reproducing information with respect to the recording medium. The arrangement is such that the recording medium and the optical head are reciprocated or rotatively moved in a track direction of the recording medium and in a direction perpendicular thereto, to execute recording/reproducing of the information.
In a conventional optical information recording and reproducing apparatus, an apparatus is generally known which is of single-track reading-out type in which a single light beam from an optical head is irradiated onto a single track, and reading-out of the information is executed by a unit of a single track.
In this method, however, a reproducing rate or speed of the information recorded on the track is determined depending on a relative speed between the optical head and the recording medium, and it has been impossible to further raise the reproducing speed. In order to solve this problem, an apparatus has been derived in which an outgoing light from the optical head is irradiated to a plurality of tracks, and reading-out of the information is simultaneously executed from the plurality of tracks. That is, the apparatus is an optical information recording and reproducing apparatus of a type which reads out a plurality of tracks. As an example, the applicant of the present invention has proposed an apparatus in which an attempt is made to reduce a number of PLL (Phase-Locked Loop) circuits and a demodulation circuit, to small-scale a data processing system, by a number of tracks read out, in Japanese Patent Laid-Open No. 2-141932/1990.
The recording medium will be described, for example, as an optical card. As shown in FIG. 6, a plurality of tracks 32 extend in an optical card 30. One of the tracks 32 is arranged by a single sector, or, as shown in FIG. 7, a plurality of sectors. The single track has an information recording area (DATA) 35 onto which writing of the information is at least executed, and a pair of ID sections 34a and 34b arranged at both ends of the information recording area 35, in which track address information and the like are recorded. In FIG. 7, the left-hand ID section 34a is used in case where the information recording area 35 is accessed from the left. On the other hand, the right-hand ID section 34b is used in case where the information recording area 35 is accessed from the right.
In connection with the above, the information recording area 35 illustrated in FIG. 7 is divided into N sectors. The sectors are so arranged as to clamp or nip therebetween buffering areas on which nothing is recorded, called a gap (GAP), in order to absorb unevenness or irregularity of a transporting or carrying speed of the optical card 30. Gaps are also provided respectively between the sectors and the ID sections.
A method of judging a track address recorded on the ID 34a or 34b will next be described with reference to FIG. 1, as an example of an optical-card recording and reproducing apparatus of single track reading-out type. The optical-card recording and reproducing apparatus reads out any one of the ID sections provided on the both ends of the track 32, and judges the track addresses on the basis of the results of the reading-out, and recording or reproducing of the information is executed with respect to the information recording area.
As shown in FIG. 1, each of the ID sections 34a and 34b has five IDs (ID.sub.0 to ID.sub.4), for example. Each of the IDs includes the same track address information, and is normally coded in error revision or correction. That is, a plurality of track addresses are written onto the ID section of the single track, that is, so-called multiple writing is executed.
In the optical information recording and reproducing apparatus, erroneous recognition of the track addresses causes the information already recorded to be broken, and erroneous information is read out. Accordingly, it is necessary to reduce the probability of the erroneous recognition of the track addresses as much as possible. For this purpose, there are five IDs. The probability of erroneous recognition is lowered by the fact that the track addresses are judged on the basis of the reading results of the five IDs.
Further, although the track addresses within each of the IDs are coded in error correction, erroneous correction may also occur. Accordingly, there are many cases where judgment of the track addresses is executed taking coincidence or agreement of the track addresses within the five IDs. For example, in a case where access is executed from the left in FIG. 1, an optical head successively scans, by the optical beam, ID.sub.0 to ID.sub.4 of the track on which there is the optical card 32 and reads out the same, and the demodulated track addresses are stored in a memory or the like. In this case, since the five IDs are completed for the first time at a time the optical beam passes through the ID.sub.4 judgment of the track addresses starts from time of the completion, as illustrated in FIG. 1.
The conventional optical information recording and reproducing apparatus of type of reading out the plurality of tracks is also so arranged as to execute judgment of the track addresses by the similar processing.
In connection with the above, it is needless to say that the apparatus of type of reading out the plurality of tracks can also be used as an apparatus for reading out a single track.
Now, as mentioned previously, in the conventional optical information recording and reproducing apparatuses of type of reading out the single track or type of reading out the plurality of tracks, judgment of the track addresses is the same in both the apparatuses. That is, judgment of the track addresses has been executed after the optical beam outgone by the optical head has passed through all the areas of the ID sections on which the track addresses are multiple-written.
In case where recording and reproducing of the information are executed with respect to the information recording areas, the above-mentioned apparatus judges whether or not the track address is a desired track address. After having judged the desired track, the apparatus recognizes a sector starting position, and must command to start recording operation or reproducing operation with respect to a recording circuit or a reproducing circuit. For this reason, judgment of the track addresses must be executed and completed within a period of time an optical spot passes through the gap portions in FIG. 7. If the judgment is not completed within the period of time, the optical spot reaches the sector starting position before starting of recognition of the sector starting position. Accordingly, it is necessary to execute the judgment of the track addresses quickly. In this connection, the fact that the optical spot reaches the sector starting position prior to the judgment means that recording/reproducing of information cannot be executed.
On the other hand, it is required for the recording medium such as an optical card that each of the gap portions is limited or narrowed as far as possible, in order to increase the memory capacity. Accordingly, there is a further need to execute the judgment of the track addresses quickly.
Execution of the judgment of the track address quickly has the following disadvantages. That is, required are the use of a high-speed CPU and accompanying speed-up of peripheral circuits, or addition of a hardware for judgment of the track addresses in the apparatus of a type for reading out the plurality of tracks. Thus, this raises the cost of the apparatus.
Furthermore, as previously described, the recording medium has been arranged such that, in order to suppress or restrain an erroneous ratio or rate of track-address recognition low as far as possible, the track addresses are multiple-written onto the single ID section within the single track. This has been the same in recording medium used for any of apparatuses of type of reading out a single track or a plurality of tracks.
However, the multiple writing has an advantage that the erroneous recognition rate of the address is lowered or reduced to improve the reliability of recording/reproducing of the information, while the multiple writing has a disadvantage that the storing or memory capacity of the information recording area of the recording medium is restricted or limited and is reduced.